RELATION OF LEAF STRUCTURE TO PHYSICAL FACTORS 75 



The only variation from the type is a slight thinning of the leaf 

 and cuticle under shade conditions. 



Light 1/8; water + 6%; humidity +(5-10%); temperature 



-(3-4). 



Pseudocymopterus anisatus 



GRAVEL: light i; available water 2.5-5.5%; humidity 30-65%; 

 temperature 55-76 : diplophyll 450/11; epidermis 40-50 /A; cuticle 

 IO/A; chlorenchym (350/4) 3 compact irregular rows prolate cells 

 next to upper epidermis, and 2 next to lower epidermis 60 /4 ; sepa- 

 rated from it by a row of horizontal cells; central water-storage 

 cells. 



PINE SHADE: light 0.05; available water 13%; humidity 40- 

 70%; temperature 48-72 : diplophyll 400/4; epidermis SO/A; 

 cuticle 2/4; chlorenchym (300/4) cells loosely arranged, third row 

 and lowermost row of prolate cells disappearing. 



The cuticle of the shade leaf is thinned, and the palisade tissue 

 is reduced in amount and more loosely arranged. 



Light 1/20 ; water +9%; humidity +(5-10%); temperature 



-(4-7). 



Gutierretzia sarothrae 



FOOTHILL MESA : light I ; available water 2-4% ; humidity 28- 

 77%; temperature 57-89 : diplophyll 500/4; epidermis 30/4; 

 cuticle IO/A; chlorenchym (440/4) compact irregular rows prolate 

 palisade cells 50-75/4, 4 rows next to upper and 3 next to lower 

 epidermis ; central water-storage tissue of globose cells. 



FOOTHILL THICKET: light 0.0125 ; available water 11% ; humidity 

 38-80%; temperature 53-85 : diplophyll 200/4; epidermis 25/4; 

 cuticle 5/4; chlorenchym (150/4) 3 rows of cells, 25 /4, next to upper 

 and 2 next to lower epidermis ; water-storage cells oblate. 



The shade-leaf and its cuticle are thinner than for the type; the 

 palisade cells have been reduced in length and in number of rows, 

 and the water-storage cells have changed from globose to oblate in 

 shape. 



Light 1/80; water +(7-9%); humidity +(3-10%); tempera- 

 ture 4. 



Euphorbia robusta 



FOOTHILL MESA : light i ; available water 2-4% ; humidity 28- 

 77%; temperature 57-89 : diplophyll 250/4; epidermis 20/4; 



